Catalytic muffling system for reducing contaminants in exhaust gases



Jan. 26, 1965 G. sLAYTER ETAL CATALYTIC MUFFLING SYSTEM FOR REDUCING CONTAMINANTS IN EXHAUST GASES 2 Sheets-Sheet 2 Filed June l0, 1960 am ML @mann E SFO rmsf YMUMM M @5V S/ GEW a s T :.Mmm 5W GWRL United States Patent Oiiee ihhh atented Jan. 26, i965 CATALYTIC MIJFFIJING SYS'IEM FR REDTUCWG CGNTAMHJAN'IS IN EXHAUST GASES G es Slayter and Wiilard I.. Morgan, Newark, Robert G. Russeil, Grmvilim and Lewis F. Schefler, Newark, (Phio, assignors to UWens-Corning Fibergias Corporation, a corporation oi Delaware Fiied .lune It), i960, Ser. No. 35,343 6 Claims. (Cl. dii-29) This invention relates to an improved exhaust system and more particularly to a muiliing system for reducing deleterious contaminants in exhaust gases issuing from internal combustion engines and also from other hydrocarbon burning devices such as gas, propane, or oil stoves and heaters.

The harmful effect of certain contaminants in exhaust gases has been known for some time, although until recently, littie progress has been made in determining their nature arid in eliminating them. Particularly in vehicle exhaust gases, it has now been determined that a combination of nitrous oxide and certain oletins react in the presence of sunlight to produce irritating smog, with propane or propylene being the most harmful of the oletins.

As the smog problem from vehicle exhaust gases has increased in recent years, the number of proposed remedies has increased proportionally with vehicle afterburuer mutiiers and catalytic muillers receiving the most serious consideration. While some mutllers proposed to date have been effective in reducing the amount of harmful constituents in exhaust gases, the amount of reduction thereof has generally been less than desirable. Further, the mutllers proposed to date tend to be quite expensive, to require frequent replacement, or both.

The present invention is based upon the discovery that titania, preferably in the form of crystalline fibers, when properly employed in an exhaust system, effectively reduces the amounts of olens, other hydrocarbons, and carbon monoxide in the exhaust gases. Effective reduction of the contaminants can only be accomplished by maintaining intimate contact between the exhaust gases and the titania fibers at the maximum temperatures available and by providing a sufficiently long period of contact to enable this reduction to take place. The reduction of the harmful contaminants is possible without the necessity for using special equipment, such as special burners or heat exchangers, and without the necessity for frequent replacement of components ofthe system.

It is, therefore, a principal object of the invention to provide an improved mufiling system.

Another object of the invention is to provide a muiiiing system which will more effectively reduce the amounts of hydrocarbons and other deleterious contaminants in exhaust gases.

Still another object of the invention is to provide an exhaust system in which exhaust gases flow through crystalline titania fibers.

Other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawings, in which:

FIG. l is a somewhat schematic view, with parts broken away and with parts in cross section, of a mutiling system embodying the principles of the invention;

FIG. 2 is a detailed View in cross section, on an enlarged scale, of a muffler used in the muiing system of FIG. 1;

FIG. 3 is a view in cross section similar to FIG. 2, illustrating a modified muiiier embodying the principles of the invention;

FIGS. 4 and 5 are views in vertical cross section of still further modications of muiflers embodying the priuciples of the invention;

FIG. 6 is a top view, with parts broken away and with parts in cross section, of a portion of an engine and a combination manifold and muffler embodying the principles of the invention;

FIG. 7 is a top View, with parts broken away and with parts in cross section, of an engine and a modied manifold-mufiler;

FIG. 8 is a view in cross section taken along the line 3 8 'of FIG. 7;

FIG. 9 is a fragmentary view, with parts broken away and with parts in cross section, of a modiied air inlet for the manifold-muffler of FIGS. 6 and 7; and

FIG. l0 is a top View, with parts broken away and with parts in cross section, of another manifold muffler.

Referring to the drawings, and more particularly to FIG. l, an internal combustion engine I@ is provided with a muiiiing system I2 embodying the principles of the invention. The system I2 basically includes manifolds 14 preferably lined with titania bers and a suitable binder, a cross-over pipe 15 and an exhaust pipe It? preferably similarly lined, a mutiier I8 containing Ya selfsupportiug body of titania fibers and a binder through which the exhaust gases pass, and a conventional tailpipe 2i) which can also be so lined, if desired. The titania fiber liners in the manifold If: and the exhaust pipe I5 serve as insulation to maintain the heat in the exhaust gases during their passage to the muffler I8 and thus enable the catalytic effect of the titania to be as great as possible. Although the titania iibers are excellent for this purpose, being highly refractory and having a high insulating eifect, it is to be understood that other high temperature insulation may be employed either within or without the manifold I4 and the exhaust pipe I6.

Air can be added to the muftlng system I2 through a pipe 2l connected with a suitable source of air such as a blower 22. The air supplies oxygen to aid further in a combustion reaction of the exhaust gases, which is effected by the catalytic action of the titania, and partieularly aids in burning the carbon monoxide in the exhaust gases. Carbon monoxide is present in a quantity varying from about 1/z% to 6%, decreasing with an increase in engine speed, and requires half as much oxygen, by volume, for its complete combustion. Enough air is usually present in the exhaust gases to compiete combustion of the hydrocarbons with the aid of the titania.

Referring to FIG. 2, .the muffler 18 in accordance with the invention includes a closed-end, cylindrical body 23 `of titania fibers aridl a binder. The cylindrical body 23 is preferabiy made of a plurality of annular segments 24 and a disc 26 to facilitate fabrication. The body 23 is centrally located in the muffler 18 by a perforate metal tube 2S, .and is held against the inlet end of the muiiier 18 by means of a metal or other non-porous wall 30 which is adjacent the porous disc 26 and is aiiixed to the perforate metal tube 2S. With this arrangement, the exhaust gases which enter an inlet connecting pipe 32, which is connected to the manifold pipe 16, must pass through the titania body 23 to an annular chamber 34 located between the perforate metal tube 28 and a casing 36 forming the Iouter housing of the muffler IS. The gases then pass inwardly through the end of the perforate tube 28 and out an outlet connecting pipe 38 which connects to the tail-pipe 2t?. The titania body 23 is extremely porous and the exhaust gases pass therethrough with very little pressure drop, .the increase in manifold pressure being almost imperceptible, usually less than 1A p.s.i.

The non-porous wall Sil, besides preventing ow of exhaust gases through the disc 26, has an important influence on the sound absorption characteristics of the mufler I8. It has been discovered that an adjusting screw 39, extending through the casing 36, can be placed in contact with the wall to vary the pressure thereon and change the tone of the muffler.

The titania body 23 includes titania crystalline particles preferably in the form of libers from 1A to 1/2" long, which can be made according to the process disclosed in Ia copending application, Serial No. 31,964, of Russell, Morgan and Scheller, tiled on May 26, 1960 now Patent No. 3,065,091. These fibers constitute but a single crystal and have been shown to be composed entirely of ti-tania, to the accuracy of X-ray diffraction analysis. Oxygen deicient titanio. fibers made in or subject to an oxygendeficient atmosphere, as more fully set forth in the Russell et al. application, supra, hav-e been found to be even more eiective as a lcatalyst and can be employed in the mufhing systems as easily yas other titania bers. The fibrous form of the titania is particularly desirable because it provides a high surface-volume ratio to enable a large surface area of titania to be presented to the exhaust gases for a given amount of the titania. The fibrous form also provides yan excellent reinforcement for the bodies in which the titania :is used, to establish great-er strength and integrity than is otherwise possible.

Eiective titania fiber bodies have been made from 87 grams of titania bers, 20 grams of wood sawdust, 25 grams of montmorillonite, and 13 grams of soda-lime glass. This mixture was combined with sutlicient water to make a mortar or paste, packed in a mold the size and shape of the segment 2d, and tired at 2500u F. to cause the glass and montmorillonite to form a binder for the titania libers and to cause the sawdust to burn out and leave an open pore or porous body. The resulting body consisted essentially of 70% titania, 20% rnontmorillonite7 and 10% soda-lime glass. By volume, the segment contained approximately 70% air, 20% titania crystalline iibers, and 10% binder (montmorillonite and the glass), with an apparent density of approximately 70 pounds per cubic foot. It is to be understood that other plastic clays such as bentonite can be used in place of the montmorillonite and that `other low melting glasses can be used in place of the soda-lime glass. Also, other discrete pieces of organic materials can be used in place of the wood sawdust. In some instances, particularly where fibers about one inch long, or longer, are used, a suciently porous body can be obtained by using the proper amount of binder, without employing any organic material.

Because at higher engine speeds the hot expanded cxhaust gases often travel through an exhaust system at speeds well above 100 miles an hour, the gases travel through the entire system in a fraction of a second and contact the -titania iibers of lthe body 23 for only a fraction of that period of time. Consequently, the body 23 must be of sutiicient size, in length, diameter, and thickness, to provide .a reasonable period of contact between the titania and the gases for a catalytic eect to occur. It may also be desired to pass the exhaust gases through the titania body more ythan one time t-o increase the period of contact therewith, a period of 0.45 second being suficient to decrease the hydrocarbons by more than 90% and a period of only 0.13 second being ample to burn substantially all carbon monoxide, if sufcient `air is present. A number of passes of the gases through the titania can be accomplished with a modified muler of FIG. 3. The mutiler 40 includes a titania body 42 which is similar to the body 23 of FIG. 2 but also has two annular baffles 44 and 46 aixed gas-tightly to a casing 48 and a circular baille in a center portion. The casing 48 can be internally lined with .titania or other high temperature insulation to minimize heat loss, the exhaust gases being at a Atemperature of 1500" F. or more during normal engine operation. A metal, non-porous wall or disc 52 is also located .at .the end of the titania body 42, and has an annular, perforate ange 54 integral therewith. The llange 54 is somewhat resilient in 4order to hold the body 42 in compression between the front of the mufer 40 and the Wall S2 when Ithe ange 54 abuts the rear of the mutller 40. With this arrangement of battles, exhaust gases entering through an inlet connecting pipe 56 pass .outwardly through the cylindrical wall ofthe ti-tania body 42, before reaching the baille 50, .to an annular chamber 58 detined by the casing 48 and the cylindrical body 42. The gases .again must pass through the cylindrical wall of the body 4:2 into the interior thereof because of the baille 46, and then pass through the body 42 a third time to another annular chamber 60 delined between the casing 48 and the body 42, because of the non-porous wall 52. Finally, the gases pass inwardly through the perforate tlange 54 and out an outlet connecting pipe 62. Thus, the exhaust gases pass through the titana body 42 a total of three times and increase their contact with the titania fibers over that possible with the mulller 18 of FIG. 2.

Air can be supplied through a supply line 63 to a chamber 64 in the mulller 40 defined by the iirst battle 44, the casing 48, and the body 42. This air passes through the heated body to the inner surface thereof, comingling and burning with the exhaust gases at a temperature above approximately 800 F. Carbon monoxide and hydro carbons are thereby reduced in the exhaust gases before they pass through the latter portions of the body i2 where they are further decreased.

While the acoustical absorption of the porous titania body in accordance with the invention is quite high, being closely comparable with conventional mufders, the muiliing effect of the bodies can be increased by making the surfaces thereof of generally conical conguration, as shown in FIGS. 4 and 5. Referring to FIG. 4, a muliler 65 includes a tirana body 66 made of the same materials as the bodies 23 and l2 of FIGS. 2 and 3, but with an annular recess 65? having a conliguration of a double truncated cone in longitudinal cross section. The recess 68 is formed by a tapered, annular wall 7l) of uniform thickness throughout its length and a centrally located, tapered proiection 72 which provides the body 66 with a cross-sectional shape similar to a W. The smaller end of the body 66 is supported centrally in the muilier 65 by an annular ceramic ring 7d. Exhaust gases entering through an inlet connecting pipe 'i6 pass through the annular wall '70 to a chamber 78 defined between a casing and the outer surface of the body 66, and, thence, iiow through a base portion 82 of the body 66 and out an outlet connect-ing pipe 84. The mufrler 65 enables the exhaust gases to make two passes through the body 66 without the necessity of employing separate batiles. The shape of the body 66 in the muffler 65 also provides a better acoustical effect due to the conguration of the tapered recess 68.

A mutller 86 of FIG, 5 includes a plurality of conical titania bodies 83 which are also very effective from an acoustical standpoint as well as from the standpoint of decreasing deleterious contaminants in the exhaust gases. The conical bodies 8S are supported in a mounting plate 90 with base ends of the bodies 8S extending therethrough so as to be in communication with exhaust gases entering the mutiler 86 through an inlet connecting pipe 92. The gases pass directly through the bodies 58 and subsequently out an outlet connecting pipe 94. A casing 96 of the muiiler S6 is preferably lined with annular titania segments 98 similar to the segments 24 of FIG. 2.

In many vehicles, a combination manifold-mulder can be used with the engine, the manifold-mulder being placed adjacent the engine to minimize opportunity for heat losses therefrom and maintain maximum temperatures. Accordingly, a combination manifold-muliler or exhaust system component l0@ (FIG. 6) can be employed adjacent each bank of four cylinders of the engine l0. The manifold-muiiler E00 contains a cylindrical titania liber body 102 held in a perforate tube ldd which is supported by ceramic rings 106 at the ends thereof. A metal plate 108 closes oil one end of the cylinder 102 and an end wall 110 of a casing 112 closes olf the other end.

Titania discs similar to the discs 26 of FIG. 2 can be employed ladjacent the plate 108 and the end wall 110, if desired, to provide an insulating eiect and to separate the exhaust gases from the metal. Short connecting tubes 114 connect the cylinders of the engine with the interior of the titania cylindrical body 102. The connecting tubes 114 contain small closed-end cylindrical bodies 116 which extend through the perforate tube 194 and the cylindrical body 102. Exhaust gases thus pass through the titania closed-end cylinders 116 upon leaving the engine cylinders, then pass through the titania body 102 and are linally exhausted through a tailor exhaust pipe 113. The interior of the titania body 102 is completely closed by the plate 108, the end wall 110, and the closed-end tubes 116 so that additional loose catalyst in the form of iibers, pellets, or crystalls can be used therein to obtain an even greater catalytic elect. The catalyst can also be used between the tube 168 and the casing 112. This catalyst can be any suitable one and may be titania crystals or pellets of the titania, montmorillonite and glass. It also can be vanadium oxide or a mixture of chromium and copper oxides, or a mixture of all three, for example. Air can be added to the interior of the body 102, if desired, through a suitably located pipe, such as a pipe 1.2i?.

Modified manifold-muiers or exhaust components 122 are shown in FIGS. 7 and 8, there being one for each bank of cylinders of the engine 10. Each of the manifoldmutliers 122 includes a porous, cylindrical, titania fiber body 124 which is similar to the bodies 23 and 4t2 of FIGS. 2 and 3. The body 124 is positioned eccentrically in a tubular casing 126 of the manifold-muffler 122 and is held in this position by spaced ceramic supports or posts 128 and 130 (FlG. 8). The casing 126 preferably has a liner 132 of titania fibers and a binder or other highly refractory, insulating material in order to lieep the casing 126 relatively cool and Vto maintain the exhaust gases at a high temperature and spaced tliereirom. The manifoldmu'ler 122 is located very close to the engine 1 0 and is connected to the individual cylinders thereof by short connecting tubes 134 which are similar to the connecting tubes 114. except that they are lined with open end cylinders 136 including titania fibers rather than the closed-end cylinders 116. Exhaust gases entering a chamber 133 defined by the titania body 121i and the liner 122 pass through the body 124 and through a center passage 1d@ to an exhaust pipe 142 (FIG. 7). With a sufficiently porous body, the passage 1d@ need not be used at all, the gases simply passing through the body in that instance. In either case, by passing the exhaust gases from the outside to the center of the body 12d as is done in the inanifold-muiller 122, a much larger ceramic surface, in this case the outer surface of the body 12d, is presented to the exhaust gases for aiding in secondary combustion as the hot exhaust gases come in contact with the body 124i. Thus, combustion can occur all over the outer surface of the body 121i. with additional air being added to the charnber 138, if necessary. With the manifold-muier 122 being 6-7 in diameter and 2l to 24 long, the body 124 is preferably about 3" thick although a thickness of about 1" is suliicient when the exhaust passage 11th is filled with loose catalyst in order to obtain suicient reaction time.

While the manifold-muffler 122 is effective in reducing oleiins, certain other hydrocarbons, and odor from the exhaust gases, carbon monoxide can be etectively removed after the gases pass through the manifold-mutiler 122 by eecting secondary combustion with excess air in the exhaust pipe 142 at the exhaust end of the manifoldmuier 122. Accordingly, a venturi shaped passage 144 is formed by a ceramic body 146 with an air passage 148 terminating at the throat of the venturi 144. Thus, the gases passing at high velocity through the tube 144 will inspirate additional air through the passage 14S due to a negative pressure established at the throat of the venturi. The combination of the exhaust gases and additional air then strike a titania ceramic cone 150 comprising titania fibers and a binder which aid in producing additional or secondary combustion of the exhaust gases thereby to complete combustion of carbon monoxide therein. A second cone 152 can be provided to further aid in secondary combustion. A liner 154 ot titania fibers and a binder can also be employed on the interior of the exhaust pipe 142 to hold heat in the exhaust gases and to aid in the combustion reaction. It is to be understood that the exhaust pipe 1412 can be employed with a conventional lined manifold in place of the manifold 122 containing the titania cylinder 12d especially where the main objective is to remove carbon monoxide from the exhaust gases.

Air for either of the manifold-mulers 106 or 122 can be supplied at each connecting tube as shown in FIG. 9. Accordingly, a connecting tube 156, which can be used in place of the tubes 114 or 134, has a ceramic liner 15S, preferably of venturi shape. An air passage is located at the throat of the liner 15S with a check valve L52 therein opening only when the respective cylinder exhausts gas and establishes a negative pressure at the venturi throat.

Each engine Cylinder can have its own exhaust system component with a manifold-muter 16d of FIG. 10 which includes a titania body 166 held in a porous or perforate metal casing 168. The casing is attached to a lined connecting tube 120 for each of the cylinders of the engine 10. Exhaust gases from the cylinder pass through the tube 170 and into a recess 172 which can be lled with loose catalyst, if desired. The gases then pass through thick walls of the body 166 and are expelled through the perforate casing 16S. An air passage 174 can -be provided if additional is desired to aid in the reaction of the exhaust gases.

It has been determined that an adequate period of Contact between regular, non-oxygen deiicient, titania crystals in the body 124 of FIGS. 7 and 8 and the exhaust gases from a V-B truck engine having a cylinder displacement of 292 cubic inches can be obtained by malring the components of the following dimensions. The casing 126 has an inner diameter of ten inches, a length of twenty-one inches, and is lined with one-half inch of insulation. The body 124 has an inner diameter of two inches and an outer diameter of 8.9 inches to provide a space having a maximum width of about 0.1 inch between the liner and the body 124. This design will provide a period of contact of 0.45 second at an engine speed equivalent to thirty miles per hour and should eliminate 90-95% of the olens. At higher speeds the period or" contact will be less but so will Abe the amounts of oleins in the exhaust gases. The temperature of the body 124i will be approximately 750 F. at idle speed, 1050 F. at an engine speed equivalent to thirty miles per hour, and 1500 F. at an engine speed equivalent to sixty miles per hour. lf loose catalyst is also used, or if oxygen-deficient titania fibers are used, the above dimensions can be reduced.

Various modifications of the above described embodiments of the invention will be apparent to those skilled in the art and it is to be understood that such modiiications can be made without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. In an exhaust system through which flow exhaust gases from an internal combustion engine, a catalyst consisting of crystalline bers of titania in the order of at least 1A in length, and means for directing exhaust gases for contact with the titania bers.

2. In an exhaust system through which ow exhaust gases from an internal combustion engine, a catalyst consisting of small particles of titania which is delicient in oxygen, and means for directing exhaust gases for contact with the titania particles.

3. In an exhaust system through which ow exhaust 7 gases from an internal combustion engine, a self-supporting porous, catalytic body consisting essentially of highly refractory crystalline fibers and a refractory, inorganic binder,`said body being located in the path of the exhaust gases.

4. A self-supporting porous, catalytic body for use in an exhaust system through which flow exhaust gases from an internal combustion engine, said catalytic body consisting essentially of titania crystalline fibers and a refractory, inorganic binder, said body being located in the path of the exhaust gases.

5. In a manifold for an internal combustion engine, Which manifold also serves as a muier therefor, said manifold including Wall means forming a manifold charnber, Wall means forming inlet passages between lsaid chamber and each of several cylinders of the engine, means forming an exhaust outlet for said chamber, and a porous body of titania fibers and a refractory, inorganic binder disposed between said inlet passages and said out- $3 let and positioned to be contacted by exhaust gases passing through the manifold.

6. An exhaust system according to claim 5 and means for supplying additional air to Said muier.

References Cited in the file of this patent UNITED STATES PATENTS 1,376,514 Clancy May 3, 1921 1,402,814 Wachtel Jan. 10, 1922 1,595,711 Cornelier Aug. 10, 1926 1,867,325 Neville July 12, 1932 1,893,372 Kryzanowsky Ian. 3, 1933 2,078,754 Day Apr. 27, 1937 2,185,584 Boyce Jan. 2, 1940 2,288,943 Eastman July 7, 1942 2,742,437 Houdry Apr. 17, 1956 2,880,079 Cornelius Mar. 31, 1959 2,991,160 Claussen July 4, 1961 

1. IN AN EXHAUST SYSTEM THROUGH WHICH FLOW EXHAUST GASES FROM AN INTERNAL COMBUSTION ENGINE, A CATALYST CONSISTING OF CRYSTALLINE FIBERS OF TITANIA IN THE ORDER OF AT LEAST 1/4" IN LENGTH, AND MEANS FOR DIRECTING EXHAUST GASES FOR CONTACT WITH THE TITANIA FIBERS. 